Impact of tidal mixing on water mass properties and circulation in the Bohai Sea: A typhoon case

Abstract

Abstract The impacts of tidal mixing on water mass properties and ocean circulation in the Bohai Sea have been comprehensively studied for the first time via diagnostic experiments for summer, winter, and typhoon cases using a high-resolution regional ocean model. The magnitude of tidal mixing estimated in the Bohai Sea is 2 orders of magnitude greater than that of the global background mixing (O (10−5) m2s−1), and the maximum reached 5 × 10−3 m2s−1. It is interesting to note that the tidal-mixing distributions are similar in summer and winter and show no obvious seasonal variations in magnitudes and patterns. In both summer and winter, tidal mixing enhances water exchange, thereby altering the water temperature and salinity distribution. However, even strong tidal mixing has an insignificant effect on the general ocean circulation pattern. An important finding is that tidal mixing-induced changes in temperature and salinity are not directly related to the intensity of mixing; instead, they are mainly associated with the vertical structures of temperature and salinity. Compared to normal weather conditions, mixing increases in typhoon weather. The variations of temperature and salinity caused by tidal mixing, however, are also mainly associated with the vertical profiles of temperature and salinity. Wind is the main factor that controls currents in typhoon weather. Tidal mixing causes significant water level changes in typhoon conditions, which is important for storm-surge forecasting.